Recently, with the help of development of technologies of information and communication, various wireless communication technologies are developing. Among the various wireless communication technologies, a wireless LAN (WLAN) is a technology enabling such a portable terminal as a personal digital assistant (PDA), a laptop computer, a portable multimedia player (PMP) and the like to access the internet in wireless in home, enterprise or an area to which a specific service is provided based on a wireless frequency technology.
In order to overcome a limit for transmission speed, which has been pointed out as a weak point of the wireless LAN, a latest technological standard introduced a system of which network speed and reliability are increased and a management distance of a wireless network is enlarged. For instance, IEEE 802.11n supports high throughput where data processing speed is greater than maximum 540 Mbps. Moreover, in order to minimize a transmission error and optimize data speed, a MIMO (multiple inputs and multiple outputs) technology using multiple antennas in both a transmitting end and a receiving end is introduced.